Porous resilient printing plate



May 23, 1944l f R. G. cHoLLAR 2,349,513

POROUS RESILIENT PRINTING PLATE Filed Feb. l2, 1942 Robert G. ChollarInventor His Attorney PatentedlMay 23, 1944 POROUS RESILIENT PRINTINGPLATE Robert G. Chollar, Dayton, Ohio, assignor to The National CashRegister Company,

Dayton,

Ohio, a corporation of Maryland Application February 12, 1942, SerialNo. 430,661

(Cl. IGI-401.1)

36 Claims.

This invention relates to resilient micro-porous printing plates and themethod of making them, and more particularly relates to suchmicro-porous resilient printing plates in which the resilient body actsas a reservoir and as a conductor for ink which is supplied to the typeface through the pores.

It is known in the art of printing that porous printing members may bemade of various materials more or less hard in structure to be used toabsorb and conduci-l ink to a printing surface inscribed thereon. Theseporous substances have been non-resilient, so that printing qualitiescharacteristic of a resilient surface equivalent to that of rubber couldnot be obtained. Heretofore, an

ink-resistant porous printing plate of suiicientl strength forcommercial use and of the fine surface porosity necessary to give evenprinting has not been produced.

This invention relates to a printing member or plate made of porousrubber or rubber-like material either of a single layer or of laminatedstructure, as will be described, said porous rubber and the process formaking it being described in my co-pending application for United StatesLetters Patent Serial No. 427,326, illed on the 19th day of January,1942.

The printing member which is the subject of this invention is aconsolidated laminated member, the main body 'of which is coarselymicroporous and the printing surface of which is nely micro-porous, thetwo layers being bonded together in such a fashion that ink passesreadily from one layer to another. Said coarser layer of the laminatedstructure is re-supplied with ink by means of a wick-like backing, whichbacking may be of porous metal, of woven fabric, of felted ber, or ofany other capillarily conducting substance.

Therefore, the principal object of this invention is to provide aresilient micro-porous printing member.

Another object of the invention is to provide a resilient micro-porousprinting member having a surface lai/er `for printing which is moreiinely micro-porous than the principal body ci the member.

Another object of the invention is to provide a resilient porousprinting member with a nonresilient porous backing.

Another object of the invention is to provide a printing member made ofmicro-porous rubber-like material which is supplied withink through acoarsely micro-porous body structure by means of a wick-like structure.

Another object of the invention is to provide a process for making theaforesaid objects.

With these and incidental objects in view, the invention includescertain novel featuresof construction and combinations of parts, theessential elements of which are set forth in appended claims and apreferred form or embodiment of which is hereinafter described withreference to the drawing which accompaniesy and forms a part of thisspecication.

In said drawing:

Fig. 1 is a cross-sectional view, in diagrammatic form. of the novellaminated resilientI porous structure and means for supplying inkthereto.

Fig. 2 is a diagrammatical perspective view, partly broken away, of atypical porous resilient laminated printing plate and of the inkingmeans therefor.

'. General description The laminated printing member is made up of afinely porous layer I0 formed of particles of raw material passing ascreen of less than 325 mesh to the inch in size, and of another layerIl, which is a coarser backing layer made up-of particles of rawmaterial passing a screen of from less than 25 to 100 mesh to the inchin size, as will .be described. The two layers merge into one another attheir juncture in such a fashion that the pores of one layerintorcommunicate with the pores of the adjacent layer, so that whateveriiuid recording material is contained in the layer Il is transmitted bycapillary action to the layer IU. The porous layer lll is made with finepores because it makes a more even impression, as the individual porestherein are not discernible by reason. of the mark deposited from 4thepore openings on recording material.

A method of making the porous rubber, although adequately described inmy co-pending application to which reference has been made, will besummarized brieily herein.

Rubber or synthetic rubber nely comminuted to the proper mesh size, saidsynthetic rubber being preferably of the butadiene co-polymer type,containing ordinary vulcanizing ingredients, is mixed parts by volumewith 45 parts by volume of a nely comminuted ller. One such mixture ismade of particles approximately less than the 325 mesh size, and onemixture is made with particles approximately less than the `25 to 100mesh size. The ner mix is made into afluid mass, like a rubber cement,by the addition of a volatile solvent such as methyl-ethylketone and isapplied to one surface of a i000- inch thick-water-soluble poly-vinylalcohol sheet, said coating being made thick enough so that when vdry itis approximately 2%000 of an inch in thickness as a maximum. sheet withthe coating thereon is placed in a die against a matrix of the printingsurface to be formed, which matrix may be of Bakelite or other materialthat will withstand pressure and heat and will not adhere to thePOU-vinyl alcohol. 'I'he uncoated side of the poly-vinyl alcohol sheetis placed next to the matrix. On top of this coating, preferably whendry, is placed the powder mix of the coarser variety so as to give thecoarser layer, when molded, a maximum thickness of between 3%000 of aninch and 12%000 of an inch. 'Ihe whole mass in the mold is compressedbetween the matrix and a ram with a pressure of between 250 pounds tothe square inch and 6000 pounds to the square inch, as the materialrequires, and then is vulcanized. The butadiene co-polymers require atemperature of about 307 degrees Fahrenheit for vulcanizing, which maybe applied either in or out of the mold. The molded plate is removedfrom the mold, and the ller, which preferably is sodium nitrate. isdissolved out by washing in a solvent which has no eect upon theresilient material used. Sodium nitrate may be washed out with hot watercontaining a wetting agent, suchas soap or one of the aliphaticpenetrants. Other iillers suggested are powdered metals, includingpowdered zinc; sodium carbonate; ammonium sulphate; or powderedwater-soluble poly-vinyl alcohol.

'Ihe sodium nitrate may be washed out of a printing plate one-tenth ofan inch thick in about two hours, if it is agitated in hot water. Thewater in the pores after a washing process is preferably replaced withink by immersing the plate. in ink above the boiling point of water,thus preventing possible adhesions of the pore surfaces. For the zinc,the carbonates, and the nitrates, acids may also be used, hydrochloricacid and dilute nitric acid being suggested. With the percentage ofingredients named, the porosity of the printing plate as a unit is about45% by volume and will absorb by volume about 45% ink. A dye ink of theoleic acid vehicle type is suitable for use with the particularsynthetic rubber mentioned.

The back of the printing plate may have bonded thereto by molding itwith the rubber mix, as a third and last layer in the mold, fabric,felt. ribbon, blotting paper, or a porous metal plate I2 to act as astrengthening support for the porous rubber and as a means to re-ink theporous rubber by means of a wick Il inserted therein.

It is to be understood that the particular materials suggested are notto limit the scope of the invention. The particular size of theparticles in the mix are specified as being best adapted for dye inkshaving an oil base. 'Ihe butadiene copolymers are resistant to corrosionby such inks.

The polyvinyl alcohol The sodium nitrate is preferred as a filler, as itmay be washed out of the molded material with hot water, which will alsodissolve any of the polyvinyl alcohol sheet that cannot be removed bypeeling. For other inks, for thicker plates, or for different moldingtemperatures, the ingredients must be selected on the basis of theirsuitability. It is within the intended scope of this invention to makesuch laminated plates with more than two layers.

In Fig. 1, the portion i4 represents a character molded in the web, thecross-sectioned portion Il showing the effect on the two layers afterbeing forced into the matrix of the character.

'I'he use of water-soluble poly-vinyl alcohol in the process describedmakes it possible to wash the polyvinyl alcohol sheet off the moldedmass as the filler is washed out to make the rubber porous.

The printing plate described is very compressible, and printing madefrom such a plate should be by very light contact, which can be assuredby surrounding the printing plate by non-resilient stops, preventingcompression of the printing plate by contact with the record material.'Ihe supply of lnk available at the type surface is so copious that alight and fast contact is all that is necessary to make a well-definedimpression. Therefore, the printing plate, not being subjected to severehammering and pressure, will last indefinitely as compared with ordinaryprinting plates, even though lthe porous structure is rather fragile ascompared with solid printing plates.

It is obvious that the laminated structure shown may be used forilltering or for separating liquids or for separating solid materialeither in gases or in liquids, or may be used for wicks for variouspurposes. The laminated structure for printing plates is, however, mostimportant if ilne printing is to be combined with high ink capacity andrapid recovery of the printing qualities after an impression. Thepreferred embodiment described produces a printing plate that willaccommodate itself to impressions less than a second apart for extendedperiods.

While the process and the product made in accordance therewith areadmirably adapted to fulfill the objects primarily stated, it is to beunderstood that the invention is directed particularly to the laminatedstructure and the process for making it. It is not intended to conne theinvention to the preferred form or embodiment herein disclosed, for itis susceptible of embodiment in various forms by varying ingredients andprocessing steps, all coming within the scope of the claims whichfollow.

What is claimed is:

1. The method of making a molded resilient web, including the step offinely comminuting rubber containing vulcanizing ingredients; the stepof comminuting to the same flneness a solid filler substance soluble bysolvents not appreciably affecting the rubber; the step of intimatelymixing the rubber and the filler substance in a lvolatile fluid to forma fluid mass; the step of applying a thin coating of the fluid mass ontoa supporting web and allowing it to dry; the step of placing thesupporting web in a mold with the uncoated side of said web next to aprinting matrix; the step of preparing a coarser dry mix of the rubberand filler; the step of applying a layer of the dry coarser mix over thecoating previously applied on the supporting web; lthe step of applyingmolding pressure to the layers of substances in the mold; the step ofvulcanizing the molded product; the step of removing the supporting webfrom the rest of the molded product; and the step of dissolving thefiller from the rubber.

2. The method recited in claim 1 wherein the rubber used is one of thebutadiene co-polymers.

3. The method recited in claim 1 wherein the rubber used is one of thebutadiene co-polymers and the filler used is sodium nitrate.

4. I'he method recited in claim 1 wherein the filler used is sodiumnitrate.

5. The method recited in claim 1 wherein approximately 55% of the rubberby volume is mixed with enough of the filler by volume to make 100%.

6. The method recited in claim 1 wherein the rubber used is a butadieneco-polymer mixed 55% by volume with sodium nitrate 45% by volume.

7. The method recited in .claim 1 wherein the volatile fluid ismethyl-ethyl-ketone.

8. The method recited in claim 1 wherein the rubber used is a butadieneco-polymer and the volatile fluid is methyl-ethyl-ketone.

9. The method recited in claim 1 wherein the supporting web used is asheet of poly-vinyl alcohol.

10. The method recited in claim l wherein the supporting web used .is asheet of water-soluble poly-vinyl alcohol.

11. 'Ihe method recited in claim 1 wherein the supporting web used isapproximately 1A000 of an inch thick.

12. The method recited in claim 1 wherein the particles oi' the finermix pass through a screen of 325 mesh to the inch.

13. The method recited in claim 1 wherein the particles of the coarsermix pass through a screen o! between 25 and 100 mesh to the inch.

14. The method recited in claim 1 wherein the particles of the finer mixpass through a screen of 325 mesh to the inch and the particles of thecoarser mix pass through a screen of between 25 and 100 mesh to theinch.

15. 'I'he method recited in claim 1 wherein the thickness of the filmleft on the supporting web after the volatilization of the volatilefluid 1s approximately 295000 of an inch.

16. 'Ihe method recited in claim 1 wherein the coarser mesh after beingmolded is of a thickness between approximately 895000 of an inch and125A000 of an inch.

17. The method recited in claim 1 wherein the molding pressure used isbetween 250 and 6000 pounds to the square inch.

18. The method recited in claim 1 wherein the matrix is of athermo-setting plastic.

19. The method recited in claim 1 wherein the matrix is of moldedBakelite.

20. 'Ihe method recited in claim 1 wherein the vulcanizing is done whilemolding pressure is applied.

2l. The method recited in claim 1 wherein the vulcanizing is done afterthe molding pressure has been released.

22. The method recited in claim 1 wherein the vulcanizing is done afterremoval of the object from the mold.

23. The method recited in claim 1 wherein the nller is sodium nitrateand the solvent therefor is hot water.

24. The method recited in claim 1 wherein the illler is dissolved inacid.

25. The method recited in claim 1 wherein the supporting web is removedby peeling.

26. The method recited in claim 1 wherein the supporting web is removedby dissolving.

27. The method recited in claim 1 wherein the coarse mix is applied tothe coating before it is dry.

28. The method of making a molded resilient porous web, including thestep of forming a laminated web of comminuted vulcanizable rubbercontaining a comminuted soluble solid tlller, the particle size of oneoutside layer of the web being finer than of other layers, and molding aprinting face on the side having the ilner layer: the step ofvulcanizing the rubber; and the step of removing the fiilr bydissolving.

29. The method recited in claim 28 wherein the rubber is a butadieneco-polymer.

30. The method recited in claim 28 wherein the ller is sodium nitrate.

31. The method recited in claim 28 wherein the ller is sodium nitrateand the solvent is water.

32. The method recited in claim 28 wherein the particles of the tlnerlayer will pass a screen of 325 mesh or more to the inch.

33. The method recited in claim 28 wherein the tlller is soluble inacids not aiecting the rubber.

34. The method recited in claim 28 wherein the molded product is bondedto a porous backing material.

35. 'Ihe method recited in claim 28 wherein the web after removal oi'theiiller is impregnated with ink.

36. The method recited in claim 28 wherein the web is placed in contactwith a wick conductor of ink.

ROBERT G. CHOLLAR.

-JERTIFI GATE 0F CO RREC TI ON.

Patent No. 2,5h9,615. May 2.5, 19h14.

ROBERT G. CHOLLAR.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correctiones follows: Page 1,second column, vline 22, strike out the words "passing s. Screen of lessthan" and insert instead --snall enough to pass a screen of; line 25,strike out in size; iines 26 and 27., for "from less than 25 to lOO meshto the inch in size" read --25 to 100 mesh to the inch or finern; page2, second column, line )49, after "to'l insert --substantially--g andthat the said Letters Patent should be read vdth this correction thereinthat the same may conform to the record of the case 1n the PatentOffice.

signed and sealed this 8th day of August, A. n. 191m.

Leslie Frazer v(Seel) Acting Commissione: of {fes-.liften

